Engine system with reversible fan

ABSTRACT

An engine system includes an engine, a primary pump coupled to the engine, and a motor fluidly connected to the primary pump. The engine system further includes a heat exchanger fluidly connected to the engine, the heat exchanger configured to accept heated coolant from the engine and deliver cooled coolant to the engine. The engine system also includes a fan driven by the motor in either a forward or a reverse mode of operation, the fan configured to pull air toward the heat exchanger in a first direction during the forward mode of operation to assist in cooling the coolant, and to push air toward the heat exchanger in a second direction opposite the first direction during the reverse mode of operation. The engine system further includes a controller configured to operate the fan in the reverse mode of operation in response to a sensed temperature of the coolant and a speed of the fan in the forward mode of operation.

TECHNICAL FIELD

The present disclosure relates generally to an engine system, and more particularly, to a method of cleaning an engine system.

BACKGROUND

Engine-driven machines such as, for example, dozers, loaders, excavators, motor graders, and other types of heavy equipment typically include a cooling system that cools the associated engine and other machine components below a threshold that provides for longevity of the machines. The cooling system typically consists of one or more air-to-air or liquid-to-air heat exchangers that reduce the temperature of the coolant circulated throughout the engine or combustion air directed into the engine. Heat from the coolant or combustion air is passed to air from a fan that is speed-controlled based on a temperature of the engine, the coolant, and/or the various components of the engine system/hydraulic fan circuit.

The cooling system fan is generally hydraulically powered. That is, a pump driven by the engine draws in low-pressure fluid and discharges the fluid at elevated pressures to a motor that is connected to the fan. When a temperature of the engine is higher than desired, the pump and motor work together to increase the speed of the fan. When the temperature of the engine is low, the pump and motor work together to decrease the speed of the fan and, in some situations, even stop the fan altogether. Under some conditions, the fan rotation can even be reversed such that airflow through the heat exchanger is also reversed to help dislodge debris that has collected in/on the heat exchanger. Such debris may restrict and/or block airflow through the heat exchanger, thereby causing the engine to operate at undesirably high temperatures.

Although known systems may reverse rotation of the fan to assist in clearing debris, such systems may not be configured to determine when the debris has been cleared. As a result, such systems may not operate the fan in the reverse direction long enough to effectively clear debris, or may operate in the fan in the reverse direction for longer than required. In either scenario, limited system resources may be inefficiently utilized. With increasing focus on the environment, particularly on machine fuel consumption, it has become increasingly important to utilize all system resources as efficiently as possible.

One system for removing debris from an engine system is described in U.S. Patent Application Publication No. 2008/0108032 to Tuhy et al., as published on May 8, 2008 (“the '032 publication”). Specifically, the '032 publication describes a heat exchanger system for a power machine. The system includes a heat exchanger, and a fan that rotates in a first/normal direction to cool hydraulic oil passing through the heat exchanger. When a sensed temperature of the oil is above a certain temperature level, the system reverses the direction of the fan for a predetermined amount of time in an attempt to clear trapped debris. Once the predetermined amount of time has elapsed, normal operation of the fan is resumed.

Although the system of the '032 publication may assist in clearing trapped debris by reversing the rotation direction of the fan, the system does not limit operation of the fan in the reverse direction based on an evaluation of system performance. In particular, the system of the '032 publication does not sense operating characteristics indicating the clearing of such debris while the fan is operating in the reverse direction. As a result, the system of the '032 publication may operate the fan in the reverse direction for longer than necessary to clear debris, thereby inefficiently utilizing system resources. In addition, the disclosed system is not configured to reverse fan direction based on a sensed fan speed or other operating characteristics of the system. Reversing operation of the fan based on, for example, coolant temperature and an additional operating characteristic such as fan speed may enable systems to determine whether the heat exchanger is blocked by debris with increased the accuracy.

The disclosed hydraulic fan circuit is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.

SUMMARY

In an exemplary embodiment of the present disclosure, an engine system includes an engine, a primary pump coupled to the engine, and a motor fluidly connected to the primary pump. The engine system further includes a heat exchanger fluidly connected to the engine, the heat exchanger configured to accept heated coolant from the engine and deliver cooled coolant to the engine. The engine system also includes a fan driven by the motor in either a forward or a reverse mode of operation, the fan configured to pull air toward the heat exchanger in a first direction during the forward mode of operation to assist in cooling the coolant, and to push air toward the heat exchanger in a second direction opposite the first direction during the reverse mode of operation. The engine system further includes a controller configured to operate the fan in the reverse mode of operation in response to a sensed temperature of the coolant and a speed of the fan in the forward mode of operation.

In another exemplary embodiment of the present disclosure, a cleaning method for an engine system includes passing coolant from an engine through a heat exchanger, and operating a fan in a forward direction pulling air toward the heat exchanger, the fan assisting in reducing a temperature of the coolant. The method also includes sensing an operating characteristic of the engine system, operating the fan in a reverse direction, opposite the forward direction, based on a speed of the fan and the sensed operating characteristic, and resuming operation of the fan in the forward direction in response to the sensed operating characteristic satisfying a return criteria.

In yet another exemplary embodiment of the present disclosure, a cleaning method for an engine system includes driving a primary pump with a combustion engine, cooling the engine with coolant passing between the engine and a heat exchanger fluidly connected to the engine, and directing a pressurized flow of fluid from the primary pump to a fan motor. The method also includes generating a first flow of air in a first direction with a fan connected to the fan motor, the first flow of air passing through the heat exchanger to assist in reducing a temperature of the coolant. The method further includes increasing a speed of the fan, sensing the temperature of the coolant while generating the first flow of air, and generating a second flow of air, in a second direction opposite the first direction, with the fan based on the speed of the fan and the coolant temperature sensed while generating the first flow of air. The method also includes sensing the temperature of the coolant while generating the second flow of air in the second direction, determining that the coolant temperature sensed while generating the second flow of air is less than a coolant temperature threshold, and generating a third flow of air in the first direction with the fan in response to the determination.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a pictorial illustration of an exemplary machine;

FIG. 2 is a schematic illustration of an exemplary engine system that may be used with the machine of FIG. 1; and

FIG. 3 is a flow chart illustrating an exemplary cleaning method of the present disclosure.

DETAILED DESCRIPTION

FIG. 1 illustrates an exemplary machine 100 performing a particular function at a worksite 110. Machine 100 may embody a stationary or mobile machine, with the particular function being associated with an industry such as mining, trash and/or waste management, construction, farming, transportation, power generation, oil and gas, or any other industry known in the art. For example, machine 100 may be an earth moving machine such as the excavator depicted in FIG. 1, in which the particular function includes the removal of earthen material from worksite 110 that alters the geography of worksite 110 to a desired form. Machine 100 may alternatively embody a different earth moving machine such as a motor grader or a wheel loader, or a non-earth moving machine such as a passenger vehicle, a stationary generator set, or a pumping mechanism. Machine 100 may embody any suitable operation-performing machine.

Machine 100 may be equipped with multiple systems that facilitate the operation of machine 100 at worksite 110, for example a tool system 120, a drive system 130, and an engine system 140 that provides power to tool system 120 and drive system 130. During the performance of most tasks, power from engine system 140 may be disproportionately split between tool system 120 and drive system 130. That is, machine 100 may generally be either traveling between excavation sites and primarily supplying power to drive system 130, or parked at an excavation site and actively moving material by primarily supplying power to tool system 120. Machine 100 generally will not be traveling at high speeds and actively moving large loads of material with tool system 120 at the same time. Accordingly, engine system 140 may be sized to provide enough power to satisfy a maximum demand of either tool system 120 or of drive system 130, but not both at the same time. Although sufficient for most situations, there may be times when the total power demand from machine systems (e.g., from tool system 120 and/or drive system 130) exceeds a power supply capacity of engine system 140. Engine system 140 may be configured to recover stored energy during these times to temporarily increase its supply capacity. This additional supply capacity may also or alternatively be used to reduce a fuel consumption of engine system 140 by allowing for selective reductions in the power production of engine system 140, if desired.

As illustrated in FIG. 2, engine system 140 may include an engine 12 equipped with a hydraulic fan circuit 10. The engine 12 may embody an internal combustion engine, for example a diesel, gasoline, or gaseous fuel-powered engine. Hydraulic fan circuit 10 may include a collection of components that are powered by engine 12 to cool engine 12. Specifically, hydraulic fan circuit 10 may include a primary pump 14 connected directly to a mechanical output 16 of engine 12, a motor 18 fluidly connected to primary pump 14 in a closed-circuit configuration, and a fan 20 connected to motor 18. Engine 12 may drive primary pump 14 via mechanical output 16 to draw in low-pressure fluid and discharge the fluid at an elevated pressure. Motor 18 may receive and convert the pressurized fluid to mechanical power that drives fan 20 to generate a flow of air in the direction of arrow 32. The flow of air may be used to cool engine 12 directly and/or indirectly by way of an air-to-air or liquid-to-air heat exchanger 28.

Primary pump 14 may be an over-center, variable-displacement or variable-delivery pump driven by engine 12 to pressurize fluid. For example, primary pump 14 may embody a rotary or piston-driven pump having a crankshaft (not shown) connected to engine 12 via mechanical output 16 such that an output rotation of engine 12 results in a corresponding pumping motion of primary pump 14. The pumping motion of primary pump 14 may function to draw in low-pressure fluid from motor 18 via a return passage 24, and discharge the fluid at an elevated pressure to motor 18 via a supply passage 26. Primary pump 14 may be dedicated to supplying pressurized fluid to only motor 18 via supply passage 26 or, alternatively, may also supply pressurized fluid to other hydraulic circuits (not shown) associated with engine 12 or machine 100, if desired. Similarly, primary pump 14 may be dedicated to drawing low-pressure fluid from only motor 18 via return passage 24 or, alternatively, may also draw in low-pressure fluid from other hydraulic circuits (not shown) associated with engine 12 or machine 100, if desired. It should be noted that, in some situations, primary pump 14 and motor 18 may be operated in a reverse flow direction and, in these situations, the fluid pressures within return and supply passages 24, 26 may be reversed.

Motor 18 may include a fixed displacement rotary- or piston-type hydraulic motor movable by an imbalance of pressure acting on a driven element (not shown), for example an impeller or a piston. Fluid pressurized by primary pump 14 may be directed into motor 18 via supply passage 26 and drained from motor 18 via return passage 24. The direction of pressurized fluid to one side of the driven element and the draining of fluid from an opposing side of the driven element may create a pressure differential across the driven element (not shown) that causes the driven element to move or rotate. The direction and rate of fluid flow through motor 18 may determine the rotational direction and speed of motor 18 and fan 20, while the pressure imbalance of the fluid may determine the torque output. In additional exemplary embodiments, the motor 18 may be a variable speed motor. In such embodiments, one or more of the pressure imbalance of the fluid and the displacement of the motor 18 may be used to determine the torque output.

Fan 20 may be disposed proximate the heat exchanger 28 and configured to produce a flow of air directed through channels of the exchanger 28 for heat transfer with coolant or combustion air therein. Fan 20 may include a plurality of blades connected to motor 18 and be driven by motor 18 at a speed corresponding to a desired flow rate of air and/or a desired engine coolant temperature. In one embodiment, a flywheel (not shown) may be connected to one of fan 20 and motor 18 to rotate therewith. In another embodiment, the flywheel may be incorporated into fan 20 (i.e., fan 20 may be oversized), if desired.

Return and supply passages 24, 26 may be interconnected via one or more different crossover passages. As shown in FIG. 2, the hydraulic fan circuit 10 may include a pressure limiting passage 34 fluidly connected to the return and supply passages 24, 26. Pressure limiting passage 34 may provide for pilot pressure control of a displacement of primary pump 14. In an additional exemplary embodiment, the fan circuit 10 may also include a makeup passage providing makeup fluid to return and/or supply passages 24, 26 to help ensure that hydraulic fan circuit 10 remains full of fluid. In a further exemplary embodiment, the fan circuit may also include a relief passage providing a leak path for high-pressure fluid within return and/or supply passages 24, 26 such that damage to the components of hydraulic fan circuit 10 caused by excessive pressures may be avoided. It is understood that one or more relief valves, check valves, and/or other known flow control devices may be fluidly connected to the pressure limiting passage 34 and/or other crossover passages. Such valves may help ensure unidirectional flows of fluid into and/or out of the respective crossover passages from return and supply passages 24, 26. It is understood that such valves may be spring-biased and at least some such valves may be solenoid-controlled.

A resolver 50 may be disposed within pressure limiting passage 34. Resolver 50 may include any type of known flow-limiting device. In an exemplary embodiment, the resolver 50 may comprise a combination of valves, filters, regulators, and/or other known flow-limiting devices connected either in series or in parallel. In an exemplary embodiment, the resolver 50 may include a first valve 52 fluidly connected to a second valve 54. The first valve 52 may be configured to connect fluid from the one of return and supply passages 24, 26 having the greater pressure with the second valve 54. In such an exemplary embodiment, the first valve 52 may be a one-way or a two-way check valve, and the second valve 54 may be a pilot pressure limiting valve. In most instances, such as when the fan 20 is operating in a normal/forward mode of operation described in greater detail below, the first valve 52 of the resolver 50 connects the pressure from supply passage 26 with such a pilot pressure limiting valve. However, when primary pump 14 and motor 18 are operating in the reverse flow direction or during an overrunning condition of motor 18, it may be possible for the pressure within return passage 24 to exceed the pressure within supply passage 26. Under these conditions, the first valve 52 of resolver 50 may move to connect the pressure from return passage 24 with the pilot pressure limiting valve. When the pressure of fluid passing through the first valve 52 of the resolver 50 exceeds a threshold limit, the pilot pressure limiting valve may move from a flow-blocking position toward a flow-passing position.

Components of the resolver 50 may be fluidly connected to a displacement actuator 60 via a fluid passage 61. For example, when the second valve 52, such as a pilot pressure limiting valve, is controlled to move toward a flow-passing position, pilot fluid utilized by the displacement actuator 60 to modify the displacement of the pump 14 may be allowed to drain to a low-pressure sump 22. Such a pilot pressure limiting valve may be configured to ensure that the pressure of the pilot fluid supplied to the displacement actuator 60, and the corresponding speed of the fan 20, may not exceed respective maximum values in the event of an unexpected malfunction of one or more pressure control valves or other pressure control components of the hydraulic fan circuit 10.

Displacement actuator 60 may embody a double-acting, spring-biased cylinder connected to move a swashplate, a spill valve, or another displacement-adjusting mechanism of primary pump 14. When pilot fluid of a sufficient pressure is introduced into one end of displacement actuator 60, displacement actuator 60 may move the displacement-adjusting mechanism of primary pump 14 by an amount corresponding to the pressure of the fluid. It is understood that one or more pressure control valves (not shown) may also be associated with the displacement actuator 60, and configured to control movement of displacement actuator 60 by varying a pressure of pilot fluid supplied to the displacement actuator 60. Components of such pressure control valves may be movable and/or otherwise controllably actuated to permit and/or restrict flow in response to a command from a controller 68. It is contemplated that such pressure control valves may be directly controlled via a solenoid.

Controller 68 may embody a single or multiple microprocessors, field programmable gate arrays (FPGAs), digital signal processors (DSPs), etc. that include a means for controlling an operation of hydraulic fan circuit 10 in response to signals received from one or more sensors 70. Such sensors 70 may be configured to sense, for example, engine temperature, coolant temperature, engine speed, fan speed, exhaust gas content, and/or other operating characteristics of the engine 12. Such sensors 70 may be, for example, any known engine sensors, pressure sensors, proximity sensors and/or speed sensors. In an exemplary embodiment, one or more of the sensors 70 may be configured to measure the rotational speed of a shaft of the fan motor 18. In further exemplary embodiments, such sensors 70 may be configured to measure a rotational speed of one or more components of the fan 20. In still further embodiments, such sensors 70 may be virtual sensors configured to determine fan speed based on, for example, a pressure of the fluid driving the motor 18. Numerous commercially available microprocessors can be configured to perform the functions of controller 68. It should be appreciated that controller 68 could readily embody a microprocessor separate from that controlling other engine- and/or machine-related functions, or that controller 68 could be integral with an engine or machine system microprocessor and be capable of controlling numerous engine and/or machine functions and modes of operation. If separate from the general engine or machine system microprocessor, controller 68 may communicate with these other microprocessors via datalinks or other methods. Various other known circuits may be associated with controller 68, including power supply circuitry, signal-conditioning circuitry, actuator driver circuitry (i.e., circuitry powering solenoids, motors, or piezo actuators), and communication circuitry.

Controller 68 may be in communication with components of both the resolver 50 and the displacement actuator 60, as well as the sensor(s) 70 and the primary pump 14, to control operations of hydraulic fan circuit 10 during at least two distinct modes of operation. The modes of operation may include a normal or “forward” mode during which primary pump 14 drives motor 18 to pull or draw air into the heat exchanger 28 in the direction of arrow 32, and a “reverse” mode in which a rotation direction of the fan 20 is reversed, thereby pushing or forcing a flow of air through the heat exchanger 28 in a direction opposite arrow 32. During the forward mode of operation, air may pass through the heat exchanger 28 to reduce a temperature of coolant passing from the engine 12 to the heat exchanger 28 via a coolant supply passage 36. Such reduced temperature coolant may then pass from the heat exchanger 28, back to the engine 12, via a coolant return passage 38. It is understood that one or more pumps or other like fluid pressurization devices may be fluidly connected to and/or otherwise associated with either of the passages 36, 38 to facilitate coolant flow, and that such fluid pressurization devices may be controllably and/or otherwise operably connected to the controller 68. During the reverse mode, trash, debris, and/or other objects 30 drawn toward the heat exchanger 30 may be cleared away by the force of the air passing through the heat exchanger in the direction opposite arrow 32. These modes of operation will be described in more detail in the following section to further illustrate the disclosed concepts.

INDUSTRIAL APPLICABILITY

The disclosed hydraulic fan circuit may be utilized with any engine system where engine cooling and/or automatic clearing of trash, debris, or other like objects 30 from the engine system 140 is desired. During the normal mode of operation, engine 12 may drive primary pump 14 to rotate and pressurize fluid. The pressurized fluid may be discharged from primary pump 14 into supply passage 26 and directed into motor 18. As the pressurized fluid passes through motor 18, hydraulic power in the fluid may be converted to mechanical power used to rotate fan 20. Fluid exiting motor 18, having been reduced in pressure, may be directed back to primary pump 14 via return passage 24 to repeat the cycle.

As fan 20 rotates, a flow of air may be generated in the direction of arrow 32 that facilitates cooling of engine 12. For example, heated engine coolant may pass from the engine 12 to the heat exchanger 28 via the coolant supply passage 36. The coolant may pass through the heat exchanger 28 and return to the engine 12 via coolant return passage 38, and the flow of air generated by the fan 20 may be pulled through portions of the heat exchanger 28 to convectively reduce the temperature of the coolant passing through the heat exchanger 28.

The fluid discharge direction and displacement of pump 14 may be regulated based on signals from sensor(s) 70 such as, for example, one or more of an engine speed signal, an engine temperature signal, an engine coolant temperature, a fan speed signal, and/or another similar signal. Controller 68 may receive these signals and reference a corresponding engine speed, engine temperature, fan speed, and/or other similar parameter with one or more lookup maps stored in memory to determine a desired discharge direction and displacement setting of primary pump 14 and a corresponding rotation direction and speed of fan 20. Controller 68 may then generate appropriate commands to be sent to displacement actuator 60 and/or the pressure limiting valve of the resolver 50 to affect corresponding adjustments to the discharge direction and/or displacement of primary pump 14.

During use, it is common for trash, debris, and other like objects 30 to be drawn toward and/or pulled proximate the heat exchanger 28 due to the flow of air created by fan 20. Such objects 30 may restrict and/or block airflow through the heat exchanger 28, thereby hindering the ability of the heat exchanger 28 to reduce the temperature of the engine coolant. Over time, the engine 12 may begin operating at temperatures higher than those for which the engine 12 was originally designed. Operating the engine 12 at such elevated temperatures may hinder the performance and durability of the engine 12, and may decrease fuel efficiency of the engine system 140. The process illustrated in the flow chart 200 of FIG. 3 may be utilized to avoid operating the engine system 140 at such temperatures.

In an exemplary embodiment, the controller 68 may intermittently and/or substantially continuously sense the temperature of the engine coolant discussed above (step: 210). One or more of the sensors 70 may assist with such temperature sensing, and such sensors 70 may be fluidly connected to the engine 12, the coolant supply passage 36, and/or the coolant return passage 38. The sensors 70 may send signals to the controller 68 corresponding to the sensed temperature, and the controller 68 may modify the fan speed to maintain a desired coolant temperature. In an exemplary embodiment, the desired coolant temperature may be maintained within a desired temperature range and/or below a desired temperature threshold. In an exemplary embodiment, such a temperature range may be defined by a single desired temperature value. In further exemplary embodiments, the temperature range may be defined by a minimum temperature threshold value and a maximum temperature threshold value. Such temperature values, and thus, the bounds of the desired temperature range, may be chosen through experimentation and/or based on the known operating characteristics of the engine 12, the coolant, the heat exchanger 28, the fan 20, and/or any other components of the engine system 140. In additional exemplary embodiments, it is understood that one or more additional operating conditions of the engine system 140 may be sensed at step 210 such as, for example, speeds, temperatures, pressures, and/or flow rates associated with one or more of the engine 12, passages 24, 26, 36, 38, motor 18, pump 14, and/or fan 20. Values corresponding to such operating conditions may also be used by the controller 68 to regulate the process illustrated in flow chart 200. For example, in addition to sensing the temperature of the engine coolant, the rotational speed of the fan 20 may be intermittently and/or substantially continuously sensed. Alternatively, the speed of the fan 20 may be determined by the controller 68 based on one or more of the control signals sent to the pump 16, the fluid pressures sent to the motor 18, the control signals sent to either the displacement actuator 60 or the pressure resolver 50, and any of the virtual sensors or maps discussed above. In such an exemplary embodiment, the fan speed may be used by the controller 68, in addition to the sensed coolant temperature, to determine whether and when to reverse the rotation direction of the fan 20. As will be described below, the controller 68 may reverse the rotation direction of the fan 20 based on two or more operating characteristics of the engine system 140, such as the speed of the fan 20 and temperature of the engine coolant. The controller 68 may reverse the rotation direction of the fan 20, for example, in response to sensing an increase in the coolant temperature while the fan 20 is operating in the forward direction at a maximum cooling speed of the fan 20. Such a maximum speed may be a predetermined speed limit of the fan 20 that is set to a desired value, below the maximum operating speed of the fan 20, to extend the useful life of the fan 20 and related components of the hydraulic fan circuit 10.

As objects 30 begin to block portions of the heat exchanger 28, the temperature of the engine coolant may gradually increase. The controller 68 may continue to monitor coolant temperature and/or fan speed, and compare the sensed coolant temperature to the desired coolant temperature range discussed above. During such a comparison, the controller 68 may determine whether the sensed temperature is within the desired coolant temperature range (step: 212). If the sensed temperature is within the desired coolant temperature range, the controller 68 may then determine whether the sensed temperature has increased such that a speed of the fan 18 should be modified (step: 214). For example, as the coolant temperature increases, the controller 68 may increase the speed of the fan 18 in order to substantially maintain a desired coolant temperature and/or in order to maintain the coolant temperature within the desired coolant temperature range. The controller 68 may increase fan speed by, for example, increasing the pressure of fluid sent to the fan motor 18 by pump 14. As described above, such an increase in pressure may be affected by controlling one or more components of the resolver 50 and/or the displacement actuator 60. If the controller 68 determines that the speed of the fan 18 should be increased and/or otherwise modified, the controller 68 may control one or more such components of the hydraulic fan circuit 10 to modify the speed of the fan 18 accordingly (step: 216).

For example, as objects 30 continue to block air flow through the heat exchanger 28, the controller 68 may continue to increase fan speed at step 216 until the speed of the fan 20 reaches the maximum cooling speed. It is also understood that during an operation cycle, the controller 68 may determine that although the sensed coolant temperature is within a desired coolant temperature range, no modification of fan speed may be required (step: 214). Regardless of whether the controller 68 has determined to modify the fan speed at step 214, the controller 68 may continue to sense coolant temperature and monitor the fan speed at step 210 after determining that the sensed temperature is within the desired temperature range.

If the controller 68 determines that the sensed temperature is above a threshold temperature of the desired coolant temperature range at step 212, and if the fan 20 is already operating at the maximum cooling speed, the controller 68 may conclude that the heat exchanger 28 is substantially blocked by objects 30 collected thereon. The controller 68 may also make such a conclusion if, for example, the fan 20 is operating at the maximum cooling speed and the sensed temperature of the coolant continues to increase. Upon making such a determination, the controller 68 may command one or more components of the hydraulic fan circuit 10 to reverse the operating direction of the fan 20 (step: 218). Thus, the decision to reverse the operating direction of the fan 20 may be made based on one or more operating characteristics of the engine system 140, such as one or both of fan speed and coolant temperature. During such a reverse mode of operation, the fan 20 may force a flow of air through the heat exchanger 28, in a direction opposite arrow 32, in an effort to remove and/or otherwise clear the heat exchanger 28 of such objects 30. The fan 20 may be driven at any desired speed below the maximum cooling speed of the fan 20 during such reverse operation. Such speeds may generate a flow of air sufficient to clear the collected objects 30.

Any of the sensors 70 discussed above, as well as the controller 68, may sense operating characteristics of the hydraulic fan circuit 10 and/or the engine system 140 (step: 220) while the fan 20 is operating in the forward and/or reverse direction. Such operating characteristics may be used by the controller 68 to determine whether and/or when to reverse the operating direction of the fan 20 and whether and/or when to return the fan 20 to the forward mode of operation. For example, the controller 68 may control the fan 20 to operate in the reversed direction for any desired/predetermined period of time in order to clear such objects 30. In an exemplary embodiment, the fan 20 may operate in the reverse direction for up to one minute in order to clear such objects 30. In additional exemplary embodiments, the controller 68 may operate the fan 20 in the reverse direction for greater than one minute to ensure such objects 30 have been cleared. In such exemplary embodiments, time may be an operating characteristic sensed at step 220.

It is further understood that such operating characteristics may include speeds, proximities, temperatures, pressures, and/or flow rates associated with one or more of the engine 12, passages 24, 26, 36, 38, motor 18, pump 14, heat exchanger 28, and/or fan 20. For example, the controller 68 may operate the fan 20 until the sensed temperature of engine coolant has been determined to be within the desired engine coolant temperature range. It is also envisioned that one or more sensors, such as a proximity sensor (not shown), may be disposed proximate the heat exchanger 28 to sense sufficient removal of such objects 30. It is further envisioned that one or more sensors may be disposed on opposite sides of the heat exchanger 28 to sense a pressure drop across the passages thereof. Alternatively, the controller 68 may receive signals from any of the sensors described above during operation in the reverse direction, and such signals may be indicative of removal of such objects 30. For example, removal of such objects 30 may result in a relatively rapid decrease in engine coolant temperature or an increase in the flow of fluid through the motor 18. In still further exemplary embodiments, such operating characteristics may comprise one or more of a temperature of working fluid and/or hydraulic fluid utilized by various components of the machine 100, a temperature of an air-to-air aftercooler and/or other additional cooling components of the machine 100, and a temperature of charge air directed to the engine 12.

Thus, the controller 68 may determine whether one or more sensed operating characteristics has satisfied a corresponding return criteria (step: 222). If, for example, a predetermined length of time has elapsed, sensed engine coolant temperature has begun to decrease, sensed engine coolant temperature has returned to the desired engine coolant temperature range, a pressure drop across the heat exchanger 28 has decreased, and/or any other known operating characteristic return criteria has been satisfied, the controller 68 may control the fan 20 to return to the forward fan direction (step: 224). If, however, such return criteria have not been satisfied, the controller 68 and/or the sensors described above may continue to sense the operating characteristics described herein (step: 220) until the return criteria have been satisfied.

It is understood that the automatic maintenance and/or fan cleaning process described with regard to flowchart 200 may be completed by the controller 68 without operator assistance and/or interaction. In addition, although the process illustrated in flowchart 200 has been described as a closed-loop process, it is understood that the exemplary processes of the present disclosure may also be operable in a variety of open-loop systems.

It will be apparent to those skilled in the art that various modifications and variations can be made to the disclosed hydraulic fan circuit. Other embodiments will be apparent to those skilled in the art from consideration of the specification and practice of the disclosed hydraulic fan circuit. It is intended that the specification and examples be considered as exemplary only, with a true scope being indicated by the following claims and their equivalents. 

1. An engine system, comprising: an engine; a primary pump coupled to the engine; a motor fluidly connected to the primary pump; a heat exchanger fluidly connected to the engine, the heat exchanger configured to accept heated coolant from the engine and deliver cooled coolant to the engine; a fan driven by the motor in either a forward or a reverse mode of operation, the fan configured to pull air toward the heat exchanger in a first direction during the forward mode of operation to assist in cooling the coolant, and to push air toward the heat exchanger in a second direction opposite the first direction during the reverse mode of operation; and a controller configured to operate the fan in the reverse mode of operation in response to a sensed temperature of the coolant and a speed of the fan in the forward mode of operation.
 2. The engine system of claim 1, further comprising a coolant supply passage extending from the engine to the heat exchanger, and a coolant return passage extending from the heat exchanger to the engine, the heated coolant passing to the heat exchanger via the coolant supply passage and the cooled coolant passing to the engine via the coolant return passage.
 3. The engine system of claim 1, further comprising a supply passage delivering fluid to the motor from the primary pump, and a return passage delivering the fluid from the motor to the primary pump.
 4. The engine system of claim 3, further comprising a pressure resolver fluidly connected to both the supply passage and the return passage.
 5. The engine system of claim 4, wherein the pressure resolver comprises a pressure limiting valve configured to selectively reduce pressure of fluid directed to the primary pump to control displacement of the primary pump during the forward mode of operation.
 6. The engine system of claim 5, wherein the pressure resolver fluidly connects the pressure limiting valve to the supply passage during the forward mode of operation and fluidly connects the pressure limiting valve to the return passage during the reverse mode of operation.
 7. The engine system of claim 5, wherein the pressure resolver connects the one of the supply and the return passage having the higher pressure with the pressure limiting valve.
 8. The engine system of claim 5, wherein the pressure limiting valve moves from a flow-blocking position to a flow passing position when pressure of fluid passing through the resolver exceeds a pressure threshold.
 9. The engine system of claim 5, further comprising a displacement actuator fluidly connected to the pressure limiting valve, the displacement actuator operable to control displacement of the primary pump during the forward and reverse modes of operation.
 10. The engine system of claim 9, wherein the displacement actuator is operable to control the speed of the fan.
 11. A cleaning method for an engine system, comprising: passing coolant from an engine through a heat exchanger; operating a fan in a forward direction pulling air toward the heat exchanger, the fan assisting in reducing a temperature of the coolant; sensing an operating characteristic of the engine system; operating the fan in a reverse direction, opposite the forward direction, in response to the sensed operating characteristic and a speed of the fan; and resuming operation of the fan in the forward direction in response to the sensed operating characteristic satisfying a return criteria.
 12. The method of claim 11, wherein the operating characteristic comprises a temperature of the coolant.
 13. The method of claim 12, further comprising sensing the coolant temperature while the fan is operating in the reverse direction, comparing the coolant temperature sensed while the fan is operating in the reverse direction to a desired coolant temperature range, and resuming operation of the fan in the forward direction based on the comparison.
 14. The method of claim 12, further comprising sensing an increase in the coolant temperature while the fan is operating in the forward direction at a maximum cooling speed, and operating the fan in the reverse direction in response.
 15. The method of claim 11, wherein the operating characteristic comprises a pressure drop across the heat exchanger.
 16. The method of claim 11, further comprising increasing a rotational speed of the fan to a maximum cooling speed prior to operating the fan in the reverse direction.
 17. A cleaning method for an engine system, comprising: driving a primary pump with a combustion engine; cooling the engine with coolant passing between the engine and a heat exchanger fluidly connected to the engine; directing a pressurized flow of fluid from the primary pump to a fan motor; generating a first flow of air in a first direction with a fan connected to the fan motor, the first flow of air passing through the heat exchanger to assist in reducing a temperature of the coolant; increasing a speed of the fan; sensing the temperature of the coolant while generating the first flow of air; generating a second flow of air, in a second direction opposite the first direction, with the fan based on the speed of the fan and the coolant temperature sensed while generating the first flow of air; sensing the temperature of the coolant while generating the second flow of air in the second direction; determining that the coolant temperature sensed while generating the second flow of air is less than a coolant temperature threshold; and generating a third flow of air in the first direction with the fan in response to the determination.
 18. The method of claim 17, wherein generating the second flow of air comprises reversing a direction of the pressurized flow of fluid.
 19. The method of claim 17, further comprising increasing the speed of the fan to a maximum cooling speed of the fan based on the coolant temperature sensed while generating the first flow of air.
 20. The method of claim 17, wherein generating the second flow of air comprises reversing a rotation direction of the fan. 